Double localized surface plasmon resonance-enhanced second harmonic generation in Al nanorod dimer structure

Abstract This study reports double localized surface plasmon (LSP)-enhanced second harmonic generation (SHG) in an aluminum nanorod (AlNR) dimer structure. The AlNR dimer comprises two AlNRs of different sizes, which are tuned to the LSP resonances of the pump light and SHG wavelengths, respectively. The SHG effects of the constituent AlNRs in single-particle states were examined for reference. The results indicated that the SHG intensity in the AlNR dimer was substantially higher than that in the AlNR monomer references. Comparing the SHG spectrum with the extinction spectra revealed that LSP resonances occurred simultaneously at the pump light and SHG wavelengths resulting in highly enhanced SHG conversion in the AlNR dimer. The surface charge and near-field distributions were calculated to demonstrate how hybridization of the plasmon modes in the constituent AlNRs produced a suitable optical field for second-order nonlinear optics.